The purpose of arc welding, like most other forms of welding, is to adhere two or more pieces of metal to each other at a specified location. This is achieved with arc welding by maintaining an electrical arc between the material to be welded and the welding material. A transformer is utilized to generate the current that is required to create and maintain such electrical arcs. Because the quality of the weld depends upon the heat that is created by the arc, most arc welding systems allow the operator to adjust the welding temperature by adjusting the transformer's output current. Because the level of a transformer's output current is proportional to the amount of magnetic flux passing through the output winding, one can vary the output current by altering the amount of flux that passes through this winding. Adjustable core shunts are commonly used to vary the magnetic path linking the primary winding to the output winding of the transformer, thereby altering the amount of magnetic flux that passes through the output winding. In turn, this allows one to vary and control the magnitude of the welding arc's current.
An effective means for controlling the position of the adjustable core shunt is to utilize a screw and nut configuration to mount the core shunt so that it may be moved among a variety of positions relative to the transformer core windings, see, e.g., Re. U.S. Pat. No. 16,012. This configuration is simple, inexpensive, and compact. However, a critical drawback of such a configuration is that the adjustment screw tends to drift because of the inherent vibration and magnetic forces to which the core shunt is subjected during normal operation. This drifting causes the shunt's position to change, which causes the welding arc current to vary. This is a significant problem, because a stable welding arc is essential for effective electrical arc welding.
One industry solution to this problem has been to utilize an adjustment screw with relatively fine threads. This approach solves the wandering problem; however, it is not desirable, because numerous turns of the adjustment screw mechanism are required to effectively adjust the position of the core shunt.
Another remedy to this problem has been to add friction enhancing components to a coarsely threaded screw configuration. This effectively reduces the drift problem, and a relatively small number of turns are required to adjust the shunt. However, with this approach, a user must apply a substantially higher amount of rotational force to adjust the core's position.
Yet another approach in solving the drift problem has been to employ vibration-damping means to reduce some of the associated forces applied to the screw mechanism. This solution is not completely effective in reducing the vibration and magnetic forces. Therefore, it does not satisfactorily reduce the drift of the adjustment screw mechanism during operation. In addition, the user is required to apply increased force when adjusting the screw mechanism to compensate for the increased resistance due to the friction-increasing, damping components. Accordingly, what is needed in the art is a mechanism for adjusting the position of a magnetic core shunt that requires minimal effort or applied force in adjusting the shunt's position, yet is capable of adequately maintaining the shunt's position when it is exposed to vibration and magnetic forces.